Exhaust fan



Sept. 1, 1936. J. M. BARRETT EXHAUST FAN Filed March 21, 19:52

INVENTOR r. H N M M s m M HJ M w Patented Sept. 1, 1936 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to the art of exhaust type ventilating fans for kitchens or other rooms where cooking odors, steam vapors, etc. are to be removed.

In its preferred form the invention forms an integral part of the pipe connection between stove and chimney (sometimes termed the flue connection). However, the invention may be applied to any room having a flue connection or outlet. While particularly adapted to cooking stoves utilizing gas, it may however be used when electricity is the heating agent and will function to remove room vapors or odors to the outside atmosphere.

Common practice is to place an exhaust type ventilator in a window opening and when such a fan is operated the vapors and odors are carried across the room and discharged to the exterior. Due to the location relative to the stove only a part of the odor-laden air is evacuated from the room. Air currents ordinarily follow the line of. least resistance in the room and some of the warmodor-laden air rises fromrthe stove and spreads throughout 'the room and house without being carried to the outside by the fan. Furthermore, during inclement weather the win- ,dow must be opened and closed each time the fan is used, or if the wind is blowing toward the window then a condition may occur where thefan will not evacuate any air from the room.

With the use of my invention the gathering point for the vapor and odors is in the immediate vicinity of their formation, and as a result the odor or vapor-laden 'air has the shortest distance to" travel before it is evacuated. The incoming air from-other parts of the room or house, moving toward the fan location, provides a blanket that helps to keep the odors from penetrating, awayfrom the stove, into the room and the remainder of the house. The use of my exhaust fan eliminates the drawing of smoke, odors and grease-laden air across the room from the'stove to a window and for this reason eliminates having dirt and scum deposits around the window and draperies.

' The use of an exhaust type fan connected to a chimney flue without proper safeguard would of itself prove more or less inefiicient and a possible hazard. For example, where gas is used as a fuel the average installation has no provision for a balanced chimney draft, so that when gusts of wind occur,'the momentary increase in the chimney draft has a tendency to snuff out pilot flames and burner flames in ovens, even when the oven is controlled by a heat regulator.

An important feature of my invention is the use of a synchronous motor for driving the fan, thereby reducing the space required for the motor and furthermore providing a noiseless driving means without sparking or eflect upon radio reception when the fan is operating.

A principal object of the invention is to provide a complete evacuating unit that becomes an integral part of the flue connection between the stove and the chimney and one that for installation requires only the removal of a section of the existing stove pipe, the insertion of the length of stove pipe containing the fan means, and then the plugging in of the electrical connection to any convenient outlet. The various adjustable elements'allow making a permanent setting of the device so that it will function satisfactorily when operating under draft conditions peculiar to each installation. When once adjusted for a fixed set of operating conditions it will stay in adjustment. The overall cost of production and manufacture is relatively small, which in turn allows a reasonable or low retail price.

In the drawing:

Fig. 1 is a partially sectioned front elevation .at C-C of Fig. 2. i

Fig. 2 is a side sectional elevation at AA of Fig. 3'.

Fig. 3 is a partially sectioned plan along the line B-B' of Fig. 2. V 7

Figs. 1, 2, and 3 are the principal views of one form of the device, whereas Figs. 4, 5, 6, and 7 show details, to an enlarged scale, of the arrangement of Figs. 1, 2 and 3.

Fig. 8 illustrates in diagrammatic fashion another preferred embodiment of the general arrangement.

The flue connection, or length of stove pipe for connection between the oven and chimney flue, is shown at I 5. The motor 9'is mounted in and protected by housings H) and I 3 so as to eliminate dirt and scum collecting on the motor; and may be connected by a conductor I4 with a source of electricity. The bearings of the motor may be oiled by the element 8 which leads from the motor bearing to the exterior of the housing I3 and having small outlets 8a. to distribute oil to each bearing. The housing I3 is attached to the flue 15 in any approved manner and is open at l9 to allow ingress of air to the fan.

A damper 6 is hinged as shown by elements 2, 3 and angularly moves around the shaft I 8. The lower end of the damper has a counterweight H which may beremovable and of suchconstruction thatits: total weight can be varied by adding to or cutting off a partrof it. The object'of the counterweight I1 is to provide the required balance for the damper 6 so that when the damper is not in an inclined position, as in Fig. 2,. it will assume a closed or semiclosed position dependent on the location of a stop I-2 and aloclring device 5. Dotted line 6a of Fig. 2 shows the damper in a vertical position or what may be termed the" closed position, and wherein the lockingxdevice 5' is shown asholding it in that position. To lock damper 6 in'anintermediate position as shown in full line in Fig. 2; the locking device 5 is turned to the dotted line position so that counterweight l1 lies substantially between l2 and b. To look damper 6' in a closed-position, counterweight H lies substantial-1y against 5c, as shown in dotted When the fanis' operating, its artificial draft causes the damper to swing partially open; and during fan-operation, the damper continuously and automatically-positions itself in a more or less inclined position-,dependent upon the relation of pressures-acting upon its faces. All variations ind-raft toward the flue outlet, whether caused by the natural or the artificial drafts, act upon the damper to cause it to automatically assume a position representative of'draft effects. By its self adjustment as to position it protects the flue inlet and likewisethe oven or ventilated space from varying effects-of the natural and/or artificial draft. The outflow'of gases past'the damper from the oven or ventilated space remains substantially constant or dependent upon the amount and temperatureof the gases tobe so ventilated; for, the areasop'ening between the flue wall and the end of the damper it varies at the same time as the effective: draftuponthis opening, so that with an increased draft and'reduced-opening the net suctiorreite'ct or flow from the oven is substantially the same.- as with full flue opening and reduced draft at; the damper outlet. I

The-embodiment includes an adjustable stop- [2 for limiting the maximum deflection or opening of the damper when the fan is operating, as in the positions i211.- or I221). Inthismanner proper opening always exists for the exit of products of combustion; the dampenbeing' counterweighted, so that when it is not held in an inclined; position due-tatheairrforce-fronr the fan, it will assume a closed position, thus closing the: opening between the insideof thefiue and theroom' proper.

Provision isals'o made for locking this tilting damper or' closure dev-ice, inan intermediate or fully closed position. This: feature will 'allow the setting fora-minimum opening of the damper so that a fixed amount of air will pass to the flue when the fan is not operating. I also-provide an automatic means forlimitingthe amount of natural-draft effective at the point of combustion when the'tilting damper is left in an unlocked tilting toward the: inside of, the flue, due to'the preferably to the two positions illustrated in Fig, 2.

the one 5 in solid line and the other 5min dotted line. i9 indicates an opening to the housing l3 through which the air enters to the fan and throughwhiclr a persons" handmay' move to grasp the locking device 5 by the projections 5b and 5c and move it from one position to another.

1 .The damper ii in its closed or dotted position 6a is shown to just'meet the projection 4 and close the opening to the housing 13. In all positions of opening, the projected height of the damper is less than the height of the opening of the housing into'the flue. Likewise baffle of Fig. 8 is shown as not extending in height completely opposite the opening of the housing into the flue.

If the damper 6 inoperatingposition, or'the ba-iile 28 extended beyond-the opening, the passage-forair from the housing to the flue would be restricted and the air from the fan would have'a tendency to mushroom and cause: back pressure upon the fan, thus cutting down its efficiency.

If no damper 6- or bafiie 29 were present in the construction, the air from the fan would impinge upon the far wall of the flue l5 and in mushrooming backwould create a downward pressure towardthe-ovenor heated space with'atendency to snuff out the flame. or force gasesout into the room.

I have found that an intermediate condition of having-the baflle, or the damper; in operating position somewhat shorter than completely coextensive with the opening is, the most practical and efficient design and have so shown Figs.

causing a.-forced draft in thatportion of the flue above the damper" 6=. This, of course, iscaused by the increase of velocity of-the air passing up the flue from the fan over that passing through the flue under natural draft conditions. The increased amount of air entering the flue from the fan and therebytheincreased air velocity, in the flue abovethe damperyalso serves to cause an induced" draft or partial vacuum in that portion of the flue= under the damper 6, and for this reason the damper 6 may be tilted and occupy'the majority of the cross sectional area of the flue I5 and atthe-same time as much or more products of combustion can pass through the area It as if the damper 6 were not'interposed across part of the cross sectional area of the flue i5- Having an increased air velocity aboye'the dampdamper. 6 will then make contact with plate 4 and in this manner close the opening which previously existed between the housing I3 and the flue l5. In some instances it may be desirable even f with the'fanirunning to have a reduced volume of air removed, and in this instance the damper 6 may be locked in anintermediate position through the use of the device 5. 7 There will also be instances. when, the fan is not runningthat an opening between the inside of the flue and its exterior will be desirable and this can be accomplished by tilting the damper 6 and holding it in its tilted position by the locking means 5.

In the average installation when the locking device is in the position shown by the full lines of Fig. 6, then with the fan blades not rotating any excess chimney draft will tend to tilt the damper 6 inward and thereby allow air exterior to the flue to enter the flue and in this way break the momentary vacuum which may exist. This function ofthe damper will eliminate the hazard of a sudden increase in chimney draft snufiing out pilot lights or flames whose products of combustion are accessible to the flue connection.

It will be observed that the action of the damper 6 is automatic when free from the locking device 5. Normally the counterweight l'l moves the damper 6 to its closed or dotted position when the fan is not running. Gases from the oven may freely pass upward through the flue I5 as in the ordinary kitchen installation. If, however, there is a sudden suction or vacuum from the chimney the damper 6 will be pulled inwardly and the tilted position will tend to protect the oven from the vacuum of the chimney and at the same time the rush of air from the room through the opening caused by the opening of the damper 6 will tend to break the vacuum. If the fan is running, the force of its ejected air will cause the damper 6 to tilt to a partly open position and a current of air as indicated by the arrows will be moved from the fan upwardly and at the same time a relatively parallel current of air will flow upward through the flue l5 at the left-hand side of the damper 6 from the oven or other connected space. Thus there will be substantially two parallel flows of air at opposite sides of the damper 6 joining above the damper 6 to form a single flow whose volume and velocity is influenced both by the natural draft suction of the chimney and by the forced draft effect of the fan. The suction at the oven, however, due to the automatic positioning of the damper 6, is not materially varied no matter what the variation is in the natural draft suction of the chimney or the forced effect of the fan.

Referring now to Fig. 8, I illustrate therein a fixed baflie 20 which fails to completely occupy the projected area of the housing I3 and serves a purpose similar to the damper 6. This may be used in place of the tilting damper and is so proportioned as to be the equivalent of the tilting damper 6 under normal conditions of operation.

Having thus described the invention, what is claimed is:

1. A system of ventilation comprising means for producing a natural draft, means for producing a flow of gases by artificial draft, the natural draft and artificial draft jointly effective in producing a second flow of gases, the two flows substantially parallel for a portion of their travel, and means automatically effective for maintaining substantially uniform the draft value of the second flow regardless of changes in value of the natural draft.

2. In combination, a chimney flue having an inlet and an outlet and having an opening in one side, a housing surrounding the opening and having an open side, fan means located within the housing and adapted to draw gases through said open side and to discharge to said flue, and means within the flue adjacent the housing and automatically eifective when the fan is operating tending to maintain the draft at the inlet to the flue constant regardless of variations in draft at the outlet of the flue.

3. In combination, a chimneyflue having an inlet and an outlet and having an opening in one side, a housing surrounding the opening and having an open side, power driven fan means located within the housing and adapted to draw gases through said open side and to discharge to said flue, and a damper within the flue adjacent the housing pivoted to swing inwardly under impact of the air from the fan and automatically effective when the fan is operating tending to maintain the draft at the inlet to the flue constant regardless of variations in draft at the outlet of the flue.

4. In combination, a section of stovepipe connected to an oven and having an opening in one side, a housing surrounding the opening and having an open side, fan means located within the housing and adapted to draw air and gases through said open side and to discharge into said stovepipe, and a bafile joining the inner wall of the stovepipe adjacent the bottom of the opening and positioned substantially opposite the opening to restrict the passage of gases from the oven past the opening thereby increasing their velocity at that point while allowing gases from the housing to enter the stovepipe at the upper end of the baflle, the baffle not extending opposite the opening to the complete extent of the opening.

JOSEPH M. BARREIT. 

